Rotating blade means for aircraft



Sept. 29, 1936. HAYS 2,055,928

ROTATING BLADE MEANS FOR AIRCRAFT Filed Oct. 8, 1954 INVENTOR.

Passe R Hays BY mm A TTORNEY Patented Sept. 29, 1936 UNITED STATESPATENT OFFICE 2,055,928 r ROTATING BLADE MEANS I08 AIRCRAFT Russell 3.Rays, Enoinitu, Calif. Application October 8, 1834, Serial-No. "7,841 8Claim. (CI. Ml-l) My invention relates to rotating blade means foraircraft, more particularly to means for varying the angles of attack ofa rotating blade at different moments of rotation. Variable ordissymmetry of airflow in connection with a direct lift propeller withrotating blade means makes it desirable that the angle of attack of theblade advancing in the direction of motion be reduced and at the sametime the retreating blade be increased in order to decrease pitching orrolling moments which would otherwise result from the directional andvelocity variations in the airflow encountered by the blades. Variousmethods and structures have been proposed and attempted to utilize airpressure variations on the blades to effect the deired variation in theblades angle of attack at different moments of rotation which have notbeen wholly successful because the lag has not been taken intoconsideration and the angle of attack variation heretofore has givenrise to either oscillation or extreme angle of attack or both. Sinceboth oscillation and extreme angle of attack are the source ofinefliciency and in many instances of instability, it is desirable thatthey be reduced or eliminated. Inasmuch as lag is the underlying sourceof the inefliciency of such angles of attack variating means, it isobvious that the reduction of lag will raise the efllciency of thestructure. Lag is the product of weight or inertia of the blade and itsrotational velocity.

It is assumed that the weight and velocity of the blade are already theminimum permitted by design and structural relations. Therefore, theprincipal and first object of my invention is broadly the provision ofmeans for reducing the lag of the aircraft rotating blade means by making a lighter portion of it directly responsive to airflow variations;

Second, to provide a means of this class which is responsive to airflowvariations by which the pitch variation is achieved in a rotating blademeans through movement of a portion only of the blade rather than theblade as a whole;

Third, to provide a pitch variation means for rotating blades in which atrailing portion of the blade is normally urged to a positive angle ofattack to the airflow by reason of resilient or tension membersconnecting the trailing portion with another portion of the blade:

Fourth, to provide a variable camber blade for a rotating blade which isdirectly responsive to airflow variations;

Fifth, to provide a pitch variating means for an aircraft rotating bladein which the lift and centrifugal forces operating on the bladesare outof alinement in vertical planes and in which the torque resultant tothis disalignment is counterbalanced by a yieldable force such as springtension in such a manner that the airflow variations effect apredetermined variation in the blades angle of attack;

Sixth, to provide a blade for an aircraft rotating blade means in whichmovable sections along the blade span effect pitch variationsindependently of each other and in direct response to air- 10 flowvariations; and

Seventh, to provide a means of this class which is very simple andeconomical of construction, easy of installation, efllcient in itsaction and wliiich will not readily deteriorate or get out of 16 or er.

With these and other objects in view as will appear hereinafter, myinvention consists of certain novel features of construction,combination and arrangement of parts and portions as will be 20hereinafter described in detail and particularly set forth in theappended claims, reference being bad to the accompanying drawing and tothe characters of reference thereon which form a part of thisapplication, in which: v

Figure 1 is a top or plan view of a blade'such as is embodied in myinvention showing some of the parts and portions broken away tofacilitate the illustration; Fig. 2 is an enlarged sectional view takenthrough 2-2 of Fig. 1 showing some of the parts in elevation tofacilitate the illustration; Fig. 3 is an enlarged sectional view takenthrough 3--3 of Fig. 1, and Fig. 41s a dia grammatical view of a bladesection on a larger scale than that of Fig. 1 and smaller than that ofFigs. 2 and 3 and showing by dash lines a varying position of thetrailing portion of the blade and showing the forces effective upon theblade with varying airflow, and the operation of the means to behereinafter described.

Similiar characters ofreference refer to similar parts and portionsthroughout the several views of the drawing.

A drive shaft l, shown best in Fig. 1 of the drawing, is provided with ahead member 2 in the ends of which are mounted alined bolts 3 and 3which form an axis H-H for hinge hangers 4 and 4 which are secured tothe spar 5 preferably integrally, which spar 5 forms the leading edge ofthe blade; This spar 5 is provided with reduced backwardly extendingcurved hinge portions in, 5b and 50 to which the trailing edge ispivotally connected by means of pins 5d, thusproviding hinge supportsbetween the leading and trailing edges of the blade forming an axisefeach provided with forwardly extending curved portions la which areadapted to fit into curved recesses in the leading member or spar 5, asshown best in Fig. 2 of the drawing, so that the combination of themembers 5, 6, and 1 form a blade turning in the direction R.

The trailing portions 8 and I of the blade are hollow, as shown best inFigs. 2 and 3 of the drawing, and therefore very light in constructionas compared with the leading edge 5, which leading edge 5 takes nearlyall the structural stresses and a large portion of the aerodynamicstresses on the blade. Thus it will be noted that with the rotation ofthe blade the airflow will tend to aline the trailing portions 6 and Iwith the leading edge 5 in such a manner that in combination theycomprise a blade section having a neutral or very small positive angleof attack to the air flow encountered. This tendency of alinement of themembers 5, 6, and I is resisted by means of tension springs 8 and 9which are secured in holes Se in the leading member or spar 5 and actwith tension T on the blade trailing portions 6 and I and tend to forcethem out of alinement with the nose or front portion of the spar 5 andthe direction of the airflow F, shown in Fig. 4 of the drawing.

The relationship between the tension T and the lift L, Fig. 4, acting onthe trailing portions of the blade is such as to provide the blade usedas a whole with a highly efficient angle of attack to the airflowencountered at any specific moment of rotation of the blade.

It will be here noted that normally the tension T of the spring 8 willurge the trailing section I, Fig. 2 of the drawing, downwardly throughan angle B of about thirty degrees from a position in which the portion1 is raised above the line of alinement to give a negative angle ofattack in a position where the leading edge 5 is in alinement with anairflow parallel to the blade of rotation. It will be noted that thetension to be exerted by the spring or springs 8 and 9 at differentvalues of the angle B is dependent upon several factors, some of whichare the relative weights and areas of the hingedly joined portions; theposition of the hinge axis A-A; the rotational velocity of the blade;the tip speed ratio; the hinge mounting of the blade; the blade sectionused, and the rolling or pitching moment desired in said blade as awhole. It will be particularly noted that in case of the tip of theblade a solid blade section changes its pitch by reason of the meansdescribed without changing its camber. In this instance the center ofpressure travel on the section at different angles of attack may beeasily derived from known wind tunnel data. From such wind tunnel datathe varying leverage effect of .a constant lift L relative to a rockingaxis A.A is easily arrived at and the tension T will then be calculatedto balance this leverage effect at all times in such a manner as tocause the lift on the section to remain constant at all moments ofrotation. Where the blade section is comprised of two movable sectionshowever, variation with camber coincides with the variation in angle ofattack, hence it is necessary to conduct wind tunnel tests to determinethe varying leverage effect exerted by the lift L on the trailingportion of the blade before the desired tension T variation can bearrived at.

Since the center of pressure travel on the blades of different cambervaries widely at different angles of attack it follows that thecounterbalancing tension T exerted by the springs 8 or 8 or otheryieldable means may necessarily increase, remain constant, or decreasewith movement of the blade section through angle B. In other words, thetension T will vary in accordance with the leverage effect of the lifton the blade or a portion of the blade about the rocking axis A-A insuch a manner that either the resultant force or the lift L operating onthe blade as a whole may tend to remain constant or vary at differentmoments of rotation in accordance with the requirements of anyparticular design. The tension T of a spring 8, as shown, will increaseas the angle B decreases, but combinations of springs or other tensionmeans may be used in many instances.

In operation the functioning of the hinged trailing sections of theblade and the tension springs result from either velocity or directionalvariation in the airflow encountered. For instance, when the airflow F,Fig. 4, changes its relative direction and velocity to F, the lift L' onthe trailing portion of the blade decreases. The tension T of the springwhich was in equilibrium with the lift L then becomes greater, with theresult that the trailing portion of the blade moves downwardly, henceincreasing its angle of attack and consequently its lift until the liftL balances the tension T exerted by the spring in this new position.

With the change of the airflow F back to F the reverse procedure takesplace with the result that the lift on the trailing portion of the bladetends to parallel. a predetermined tension exerted by the spring throughthe distance travelled.

The effectiveness of such a pitch variation means is based upon twobasic premises. First, that the necessary weight of the blade can bemassed in the spar 5 which takes the drive torque and strongestaerodynamic forces; thus the trailing portion of the blade is many timeslighter than the blade as a whole. Second, that although the springexerts a strong tension giving the blade shape, and transmitting thelift on the trailing portion to the heavier structure of the spar, suchyielding means have relatively little weight, thus since weight is theprimary source of lag and since the lift of the blade as a whole isdirectly responsive to the varying camber and angle of attack effect ofthe hinged lighter portion, it follows that the blade as a whole is muchmore responsive to variations in the velocity and direction of airflowencountered.

With rigid sections such as are at the tip of the blade the rockingaction about a radially extending axis is much more responsive to atension means opposing airflow variations than to airflow variationsopposed to weight distribution of the blade about a fixed axis augmentedby the use of pilot planes which must necessarily be out of phase andalso limit the responsive action of the blade to such airflowvariations.

Furthermore, since the airflow and velocity variations do not occuruniformly along the span of the blade, it follows that the movabletrailing portions 6 and 1 will react differently and independently inavoiding extreme angles of attack, thus raising the efliciency of theblade as a whole and it is readily seen that any number of such sectionsmay be used.

In the present instance, the blade described is used in combination witha hinge mounting,

the axis of the hinge making an acute angle C, as shown best in Fig. 1,with the leading edge of the blade. However, it will be seen from theforegoing that such a means of providing a variable camber and pitch issubject to wide variation in application and may be advantageously usedupon all types of rotating blade structures.

Though I have shown and described a particular construction, combinationand arrangement of parts and portions, I do not wish to be limited tothis particular construction, combination and arangement but desire toinclude in the scope of my invention the construction, combination andarrangement substantially as set forth in the appended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a sustaining rotor for aircraft, a blade consisting of a leadingedge portion, a plurality of trailing edge portions in independentpivotal relation therewith, and yieldable means connecting said leadingedge portion with said trailing edge portions whereby separate sectionsmay adjust themselves in relationship with the air velocity at theirrespective locations with a minimum of lag.

2. In a sustaining rotor for aircraft, a blade consisting of a leadingedge portion, a plurality of trailing edge portions in independentpivotal relation therewith, and yieldable means connecting said leadingedge portion with said trailing edge portions tending to hold saidtrailing edge portions in certain relative pivotal relation with saidleading edge portion, said trailing edge portions being not more thanone half as heavy as the leading edge portion, whereby separate sectionsmay adjust themselves in relationship with the air velocity at theirrespective locations with a minimum of lag.

3. In a sustaining rotor for aircraft, a blade consisting of a leadingedge portion, a plurality of trailing edge portions in independentpivotal relation therewith, and yieldable means connecting said leadingedge portionwith said trailing edge portions tending to hold saidtrailing edge portions in certain relative pivotal relation with saidleading edge portion, said trailing edge portions being not more thantwo times as wide as the leading edge portion, whereby separate sectionsmay adjust themselves in relationship with the air velocity at theirrespective locations with a minimum of lag.

4. In a sustaining rotor for aircraft, a blade consisting of a leadingedge portion, a plurality of trailing edge portions in independentpivotal relation therewith, and yieldable means connecting said leadingedge portion with said trailing edge portions with varying springtensions at diflerent sectons whereby separate sections may adjustthemselves in relationship with the air velocity at their respectivelocations with a minimum of lag 5. In a sustaining rotor for aircraft, ablade consisting of a leading edge portion, a plurality of trailing edgeportions in independent pivotal relation therewith, and yieldable meansconnecting said leading edge portion with said trailing edge portionswith varying spring tensions at different sections, said spring tensionsincreasing as the individual trailing sections approach the blade tipwhereby separate sections may adjust themselves in relationship with theair velocity at their respective locations with a minimum of lag.

6. In a sustaining rotor for aircraft, a blade consisting of a leadingedge portion, a plurality of trailing edge portions in independentpivotal relation therewith, and yieldable means connecting said leadingedge portion with said trailing edge portions with varying springtensions at diil'erent sections, said spring tensions increasing as theindividual trailing sections approach the blade tip, said trailing edgeportions being not more than one half as heavy as the leading edgeportion and not more than twice as wide, whereby separate sections mayadjust themselves in relationship with the air velocity at theirrespective locations with a minimum of lag.

7. In a means of the class described, a blade comprising an elongatedleading edge portion rev- Oluble about an axis at right angles to itsdirection'of elongation, a trailing edge portion in pivotal relationwith the rear side thereof, said trailing edge portion being not morethan one half the weight of the leading edge portion, and tension meanstending to support said leading edge portion and said trailing edgeportion in angular relation to each other and variable with the variablepressure exerted thereon.

8. In a means of the class described. a blade comprising an elongatedleading edge portion revoluble about an axis at right angles to itsdirection of elongation, a trailing edge portion in pivotal relationwith the rear side thereof,

said trailing edge portion being not more than twice the width of theleading edge portion and tension means tending to support said leadingedge portion and said trailing edge portion in angular relation to eachother and variable with the variable pressure exerted thereon.

RUSSELL R. HAYS.

